After transforming the subdwarf photometry to the ACS/WFC system and correcting the subdwarf metallicities, we fitted the cluster main sequences in a F814W\(_0\)  vs. (F606W-F814W)\(_0\)  CMD with the subdwarfs. To this end, we
vary the assumed cluster distance modulus until the error-weighted difference between the subdwarfs and the previously determined main-sequence ridgeline are minimal. Due to the steepness of the cluster ridgelines and the accurate Gaia parallax distances,
this essentially results in minimizing the error weighted color differences between the subdwarfs and the main sequence ridge lines. We exclude subdwarfs with \(M_{814}<4\)  from the fits since these could already have evolved away from the
main sequence. We also exclude subdwarfs with discrepant photometry since these could be undetected binaries. Fig. REF  shows examples of our subdwarf fits for four globular clusters. The clusters shown are the same
as the ones depicted in Fig. 2 of [1]}. We will derive an error bar for the subdwarf distance moduli in sec. 3 when we compare the subdwarf distance moduli against literature data.
